Plug slip ring with retaining mechanism and method

ABSTRACT

A downhole tool for sealing a well includes a push ring; a first slip ring located adjacent to the push ring; a first wedge located adjacent to the first slip ring and configured to push the first slip ring and separate the first slip ring into parts; and a retaining mechanism configured to retain the first slip ring next to one of the push ring or the first wedge. The retaining mechanism is part of either (1) the first slip ring or (2) the one of the push ring or the first wedge, but not both.

BACKGROUND Technical Field

Embodiments of the subject matter disclosed herein generally relate to downhole tools related to perforating and/or fracturing operations, and more specifically, to a plug having a retaining mechanism.

Discussion of the Background

In the oil and gas field, once a well 100 is drilled to a desired depth H relative to the surface 110, as illustrated in FIG. 1, and the casing 102 protecting the wellbore 104 has been installed and cemented in place, it is time to connect the wellbore 104 to the subterranean formation 106 to extract the oil and/or gas. This process of connecting the wellbore to the subterranean formation may include a step of plugging the well with a plug 112, a step of perforating the casing 102 with a perforating gun assembly 114 such that various channels 116 are formed to connect the subterranean formations to the inside of the casing 102, a step of removing the perforating gun assembly, and a step of fracturing the various channels 116.

Some of these steps require to lower in the well 100 a wireline 118, which is electrically and mechanically connected to the perforating gun assembly 114, and to activate the gun assembly and/or a setting tool 120 attached to the perforating gun assembly. Setting tool 120 is configured to hold a plug 112 prior to plugging the well. FIG. 1 shows the setting tool 120 disconnected from the plug 112, indicating that the plug has been set in the casing and the setting tool 120 has been disconnected from the plug 112.

FIG. 1 shows the wireline 118, which includes at least one electrical connector, being connected to a control interface 122, located on the ground 110, above the well 100. An operator of the control interface may send electrical signals to the perforating gun assembly and/or setting tool for (1) setting the plug 112 and (2) disconnecting the setting tool from the plug. A fluid 124, (e.g., water, water and sand, fracturing fluid, etc.) may be pumped by a pumping system 126, down the well, for moving the perforating gun assembly and the setting tool to a desired location, e.g., where the plug 112 needs to be deployed, and also for fracturing purposes.

The above operations may be repeated multiple times for perforating and/or fracturing the casing at multiple locations, corresponding to different stages of the well. Note that in this case, multiple plugs 112 and 112′ may be used for isolating the respective zones from each other during the perforating phase and/or fracturing phase.

These completion operations that involve the plug-and-perf multistage fracturing method, use composite plugs pumped downhole with water and set in place to isolate the stages. The composite plugs ensure that the fracturing fluids are directed into a specific stage. These operations are becoming the preferred method in the industry. In this regard, it is believed that more than 80 percent of hydraulically fractured wells employ plug-and-perf completions. This is so because this method is more economical and the technique offers greater flexibility in designing and pumping stimulation jobs.

Equipped with this technique, the well operators can deploy logging techniques to identify the most productive zones along the casing and then change the plug-and-perf program as necessary, to deploy plugs at the intervals targeted for perforating and completion. The number of plugs and the distance between the plugs can be changed on the go.

The sliding sleeve completion tool cannot offer this degree of flexibility to allow fracturing fluids to selectively fracture zones in the formation. The sliding sleeve completion tools are advantageous due to the reduced rig time, faster operations and limited water usage. However, because the sleeves are installed with the casing, the sleeves cannot be moved once a casing string is installed.

However, composite plugs that are used for the completion of the wells have their own limitations. For example, a frac plug 200 shown in FIG. 2 has a mandrel 202 on which the following elements are added: a top push ring 203, upper slip ring 204, upper wedge 206, sealing element 208, lower wedge 210, lower slip ring 212, a bottom push ring 216 and a mule shoe 218. When the setting tool (not shown) presses on the push ring 203, the intermediate components press against the mule shoe 218, causing the sealing element 208 to expand radially and seal the casing. Upper and lower wedges 206 and 210 press on their corresponding slip rings 204 and 212, separating them into plural parts and at the same time forcing the separated parts of the slip rings to press radially against the casing. In this way, the slip rings secure the plug in place and the sealing element seals the well. If the mandrel has a bore (not shown), internal fluid of the well may pass through the plug.

In one application, a ball 220 may be released inside the well to seal the internal bore of the mandrel. In another application, the mandrel may have no bore, in which case the plug is a bridge plug that fully seals one region from the other inside the well.

The slip rings discussed above may be manufactured as a continuous ring, with slots which should help the rings to break up into multiple pieces when the plug is set. In theory, each slip ring 204 and 212 would ride up on the adjacent wedge 206 and 210, respectively, as the top push ring 203 is compressed toward the mule shoe 218 during the setting operation. In cross-section, the inner surface of the slip ring is typically configured with an angle to match that of the wedge or ramp ring, and a flat portion to match the mandrel. As the slip rings ride up the corresponding wedges, they would ideally break apart from each other into individual parts 204A, which would then be evenly spaced around the casing 230, as illustrated in FIG. 3. FIG. 3 also shows the uniform spaces 232 between the individual parts 204A, the wedge 206 pressing against the parts 204A, mandrel 202 and bore 201 formed inside the mandrel 202. This configuration grippingly engages the casing 230 and holds the plug 200 in place in the set position.

A continuous slip ring as illustrated in FIG. 2 is known as “one-piece slip.” A one-piece slip is difficult to break apart, and therefore robust during the operation of running the plug in the hole. This robustness is an advantage, as it helps to prevent a failure known as plug preset. A plug preset happens when a jar or obstacle in the well interferes with the advancement of the plug in the bore of the well. The obstacle causes the slip ring or subset of slips to break open and grab the casing before the plug arrives at its intended depth. Once a plug is partially preset, it typically must be fully set to disengage the setting tool, and then milled out with an expensive and time consuming coiled tubing operation. The continuous ring is also fairly easy to handle and install during manufacture, as the rings are easily tracked, stored and stacked. The continuous ring can be pressed in a direct mold, and then machined with holes for the ceramic buttons and preferential slots to encourage even breakage. This process does require a milling operation. More commonly, it is machined from wrapped material.

The one-piece slip has the disadvantage that, initially, does not break at every weak section. It often may break into two sections during the initial set, before being finally broken at each weak point during full set. This partial break often leaves large gaps 232B between some adjacent slips elements 204A and smaller gaps 232A between others, as illustrated in FIG. 4 (FIG. 4 omits, for simplicity, to show the wedge and mandrel). This uneven set up results in uneven gripping, and sometimes plug failure.

Another slip design uses individual, or segmented slips. Plugs with individual slips typically use a retaining band to hold the slips in place until the setting operation is performed. The slips can be individually molded or likewise machined from a band of wrapped material. They typically must be held by hand or with a jig during assembly, and then the retaining band installed. Individual slips can be placed more uniformly during the setting operation. This kind of plug may also incorporate individual ramps on the setting wedge to space the slips. The retaining band is a weak way of holding the slips, however, and can break prematurely. Plugs with retaining bands are more likely to be preset inadvertently. In addition, the band can be caught between the slip and the casing, which can prevent the plug from setting correctly, and may reduce the pressure holding capacity of the plug. Similar disadvantages are present for other types of plugs, for example, a big bore plug that has no mandrel and requires no milling. In fact, the problems discussed above are typical to any plug having slip rings.

Thus, there is a need to provide a better plug that distributes the slip ring parts more uniformly along the casing, when the plug is set.

SUMMARY

According to an embodiment, there is a downhole tool for sealing a well, the downhole tool including a push ring; a first slip ring located adjacent to the push ring; a first wedge located adjacent to the first slip ring and configured to push the first slip ring and separate the first slip ring into parts; and a retaining mechanism configured to retain the first slip ring next to one of the push ring or the first wedge. The retaining mechanism is part of either (1) the first slip ring or (2) the one of the push ring or the first wedge, but not both.

According to another embodiment, there is a downhole tool for sealing a well, the downhole tool including a mule shoe; a first slip ring located adjacent to the mule shoe; a first wedge located adjacent to the first slip ring and configured to push the first slip ring and separate the first slip ring into parts; and a retaining mechanism configured to retain the first slip ring next to one of the first wedge and the mule shoe. The retaining mechanism is part of either (1) the first slip ring or (2) one of the first wedge and the mule shoe, but not both.

According to still another embodiment, there is a downhole tool for sealing a well, the downhole tool including a push ring; a first slip ring located adjacent to the push ring; a first wedge located adjacent to the first slip ring and configured to push the first slip ring; a sealing element for sealing the well and located adjacent to the first wedge; a second wedge located adjacent to the sealing element; a second slip ring located adjacent to the second wedge; a mule shoe located adjacent to the second slip ring; and a retaining mechanism configured to connect at least one of the first slip ring and the second slip ring to one of the push ring, the first wedge, the second wedge and the mule shoe. The retaining mechanism is part of either (1) the first slip ring or the second slip ring, or (2) one of the push ring, the first wedge, the second wedge or the mule shoe, but not both.

According to yet another embodiment, there is a downhole tool for sealing a well, the downhole tool including a slip ring located on a mandrel; a wedge located adjacent to the slip ring; a retaining mechanism located adjacent to the slip ring and configured to maintain the slip ring attached to the mandrel; and an element located adjacent to the retaining mechanism. The retaining mechanism is independent of the slip ring, the wedge and the element.

According to another embodiment, there is a method for using a plug in a well, the method including providing the plug with a retaining mechanism located between a slip ring and one of a wedge, mule shoe and push ring; lowering the plug into the well; and setting the plug into the well by activating a setting tool, which results in parts of the slip ring to move away from each other. The retaining mechanism is configured to guide the parts of the slip ring to maintain a substantially uniform gap between the parts.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:

FIG. 1 illustrates a well and associated equipment for well completion operations;

FIG. 2 illustrates a traditional composite plug;

FIG. 3 illustrates an ideal distribution of slip ring parts when the plug is set;

FIG. 4 illustrates an actual distribution of the slip ring parts when the plug is set;

FIG. 5 illustrates a plug having a retaining mechanism;

FIG. 6 is a cross-section of a plug having a retaining mechanism;

FIG. 7A illustrates a part of the plug having the retaining mechanism;

FIG. 7B illustrates the retaining mechanism;

FIG. 8A illustrates another part of the plug having the retaining mechanism;

FIG. 8B illustrates the retaining mechanism;

FIGS. 9A to 9D illustrate other possible locations of the retaining mechanism;

FIG. 10 illustrates a plug having two retaining mechanisms;

FIG. 11 illustrates still another retaining mechanism;

FIG. 12 illustrates yet another retaining mechanism;

FIG. 13 illustrates a retaining mechanism combined with a breaking mechanism;

FIGS. 14A-14D illustrate a retaining mechanism being combined with a band;

FIG. 15 is a flowchart of a method for manufacturing a plug having a retaining mechanism; and

FIG. 16 is a flowchart of a method of using a plug having a retaining mechanism.

DETAILED DESCRIPTION

The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to a composite plug. However, the embodiments discussed herein are applicable to other plugs, e.g., a big bore plug.

Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

According to an embodiment illustrated in FIG. 5, a composite plug 500 includes a mandrel 502 having a bore (not seen in this figure), a push ring 503, an upper slip ring 504, an upper wedge 506, a sealing element 508, a lower wedge 510, a lower slip ring 512, and a mule shoe 518. These elements are added to the mandrel 502 in this order. A slip ring is understood in the following to refer to (1) a one piece slip, or (2) partially segmented slips that are mostly not connected to each other, but are retained in a ring shape by certain connection points, or (iii) fully segmented slips that are not connected to each other at all, but are retained in a ring shape as they are connected by the alignment feature or (4) any combination of one piece slip and the partially or fully segmented slips. Mule shoe 518 is attached with pins 521 to the mandrel and mandrel 502 is attached with pins 522 to the setting tool (not shown). After the plug 500 is set (the figure shows the plug before being set), the setting tool is pulled away from the plug until the pins 522 break away and thus, the plug is disconnected from the setting plug.

FIG. 5 shows that at least one slip part 504A of the upper slip ring 504 is held in place by an upper retaining mechanism 530, which may be located on the push ring 503, or on the upper wedge 506 or on each of the push ring 503 and the upper wedge 506. The upper retaining mechanism may be part of the upper slip ring, or the push ring or the upper wedge or any combination of these three elements. While the slip ring 504 may be a continuous slip ring, it also may be formed of individual parts. Thus, the slip ring parts 504A may be held together with a band or formed continuously into a ring. Another retaining mechanism 540 may held in place a slip part 512A of the lower slip ring 512. The lower retaining mechanism 540 may be located on the mule shoe 518, or on the lower wedge 510 or on each of the mule shoe and the lower wedge. The lower retaining mechanism 540 may be part of the lower slip ring, or the mule shoe or the lower wedge or any combination of these three elements. While FIG. 5 shows the upper and lower retaining mechanisms 530 and 540 to be located outside the plug, these retaining mechanisms are actually located inside the plug, as now discussed.

FIG. 6 shows a cross-section of the plug 500 of FIG. 5. The bore 501 of the mandrel 502 is now visible and also a ball 520 that blocks the downward flow of the fluids in the well. FIG. 6 also shows each slip ring having plural protuberances 505 and 513 that are configured to engage (bite into) the casing. According to this embodiment, the retaining mechanism 530 (note that the invention is applicable when only one of the slip rings has the retaining mechanism; however, the figures and discussion herein presents a retaining mechanism for each slip ring for completeness) is part of the push ring 503. In one embodiment, the retaining mechanism 530 is integrally made with the push ring 503, as illustrated in FIG. 7A. In another embodiment, the retaining mechanism 530 may be attached to the push ring 503 (for example, with a screw) after the push ring is manufactured. In one embodiment, the push ring 503 has plural retaining mechanisms 503-1 to 503-4, as shown in FIG. 7B. In one application, the push ring may have as many retaining mechanisms as the number of slip ring parts 504A. In another application, the push ring may have a retaining mechanism for every second slip ring part. In still another application, the number of parts “m” of the retaining mechanism formed on the push ring is smaller than the number “n” of slip ring parts. In yet another application, the retaining mechanism is a single circular element that contacts each slip ring part. In one application, the push ring is made of a composite material and the retaining mechanism is made of a metal. In another application, both the push ring and the retaining mechanism are made of a composite material.

Similar to the embodiments of FIGS. 7A and 7B, the retaining mechanism 540 may be integrally made with the mule shoe 518 as illustrated in FIG. 8A, or the retaining mechanism 540 may be added to the mule shoe 518, for example, with a pin. In both embodiments, the corresponding slip ring part 504A and 512A has a recess 504B and 512B, respectively, for receiving the retaining mechanism. As illustrated in FIG. 8B, the mule shoe 518 may have plural retaining mechanisms 540-1 to 540-4. In one application, the mule shoe may have as many retaining mechanisms as the number of slip ring parts 512A. In another application, the mule shoe may have a retaining mechanism for every second slip ring part. In still another application, the number of retaining mechanisms formed on the mule shoe is smaller than the number of slip ring parts. In still another application, the number of parts “m” of the retaining mechanism formed on the mule shoe is smaller than the number “n” of slip ring parts. In yet another application, the retaining mechanism is a single circular element that contacts each slip ring part. In one application, the mule shoe is made of a composite material and the retaining mechanism is made of a metal. In another application, both the mule shoe and the retaining mechanism are made of a composite material.

Note that in one embodiment, only one of the push ring and mule shoe has the retaining mechanism. In still another application, both the push ring and the mule shoe have the retaining mechanism. In still another application, the push ring has plural retaining mechanisms and the mule shoe has only one retaining mechanism. In yet another application, the push ring has only one retaining mechanism and the mule shoe has plural retaining mechanisms. One skilled in the art would understand that any number of retaining mechanisms on the push ring and/or the mule shoe is possible.

The embodiments discussed with regard to FIGS. 6 to 8B may have the retaining mechanism (530 or 540) molded into the upper or lower wedges and/or mule shoe or any other part adjacent to the slip rings. For example, as illustrated in FIG. 9A, a retaining mechanism 542 may be attached/molded into the corresponding wedge 510 and this retaining mechanism engages a corresponding shoulder 512C of the ring slip 512. The same configuration may be used for the slip ring 504, with the retaining mechanism 542 being part of the upper wedge 506. In another embodiment, as illustrated in FIG. 9B, the retaining mechanism 542 may be hidden from sight, i.e., it may be located at a tip of the wedge 510, under the slip ring 512. In still another embodiment, as illustrated in FIG. 9C, the retaining mechanism 542 may be located between the tip and the top of the wedge 510, at an interface between the slip ring and the wedge. In yet another embodiment, the retaining mechanism 542 is not part of the wedge, but rather is a band that fits in corresponding groove 512C in the slip ring and groove 510A in the wedge 510, as illustrated in FIG. 9D. Although the retaining mechanism 542 has been discussed above as being located between the slip ring and the wedge, it is possible to use the configurations shown in FIGS. 9A to 9D for locating the retaining mechanism 542 between the slip ring and the mule shoe, or the slip ring and the push ring. In one embodiment, the retaining mechanisms 530, 540 or 542 may be a band, a tongue and groove, or a tab that holds one or more individual slip ring part in place. FIGS. 7A and 8A show the retaining mechanism being positioned perpendicular to the expected motion of the slip ring during the setting operation. This retaining mechanism could be made of the same material as the push ring, the wedge, or mule shoe, (typically glass filled thermoset composite) or it could be some softer but more durable material, such as a thermoplastic or elastomer material, which could be overmolded or installed. In one application, the retaining mechanism could snap onto features on the push ring, mule shoe or wedges, if built separately. In still another application, the retaining mechanism may be attached to each slip ring part.

In another embodiment, as illustrated in FIG. 10, there are two retaining mechanisms for a given slip ring part 512A, a first retaining mechanism 540 associated with the mule shoe 518 and a second retaining mechanism 542 associated with the corresponding wedge (510 in this case) of the slip ring part. The structure of each of the first and second retaining mechanisms in this embodiment may be similar to the embodiment discussed in FIG. 8A or FIG. 9A.

Note that in all these embodiments, although the retaining mechanism contacts the slip ring, the retaining mechanism is not made integrally with both (1) the slip ring and (2) anyone of the other components of the plug, i.e., the mule shoe or the wedge or the push ring. In other words, (i) the combination of the mule shoe and the lower slip ring, or (ii) the combination of the push ring and the upper slip ring, or (iii) the combination of the slip ring (upper or lower) and the corresponding wedge is made of separate components, although these components are located next to each on the mandrel 502. Thus, if someone decides to remove one of these elements from the mandrel, this action can be performed without breaking the retaining mechanism. However, it is possible to make one of the slip ring (the lower, the upper or both) integral with a breakable element, for example, an aligning element, which aligns the various parts of the slip ring (note that the slip ring may include individual elements that are hold together by the alignment element) relative to the mandrel. The aligning element may also guide the various parts of the slip ring, after they separate, as the corresponding wedge is pushing them. In one application, the alignment element may be one of the retaining mechanisms discussed herein.

In one embodiment illustrated in FIG. 11, the retaining mechanism 550 is made as an interlocking mechanism, i.e., one part 550A of the retaining mechanism 550 is part of the wedge 510 (or 506) and the other part 550B of the retaining mechanism 550 is part of the slip ring 512 (or 504). The retaining mechanism 550 may be shaped as a tongue and groove connection between the wedge and the slip ring. FIG. 12 shows the tongue 550A and groove 550B for this configuration, with the tongue attached to the wedge 510 and the groove formed into the slip ring. This connection could also be T shaped, L shaped, Dove Tailed, or any other interlocking feature. The protrusion 550A from the wedge 510 could be molded or machined, or created in a separate manufacturing step and then installed or overmolded on to the wedge 510.

Different from the embodiments illustrated in FIGS. 7A to 8B, the tongue and groove connection of the present embodiment would extend in line with the expected motion A of the slip ring during the setting operation and would be additionally able to act as a guide for the one or more slip ring parts. In this way, the retaining mechanism not only maintains the slipping parts together, but also helps to space the slip ring parts apart, in a controlled manner, i.e., uniformly.

In one application, the guiding groove 550B in FIG. 12 could also be not completely constrained within the slip ring part, and could also be reversed, with the slip ring having the protrusion 550A and the wedge 510 having the groove 550B. Either part could also contain a second tab positioned perpendicular to the motion, which would be required to break before the slip could deploy.

According to another embodiment illustrated in FIG. 13, a plug 1300 includes a one-piece slip ring 512 (or 504) that is used in conjunction with a breaking element 560, which is incorporated into the mule shoe 518 (or push ring 503), or into any other part adjacent to the flat end of the slip ring 512. The breaking element 560 could be a band made out of ceramic or composite. The one-piece slip ring 512 would be connected to itself by a thin connecting element 562. In other words, the thin connecting element 562 links together all the slip ring parts 512A. The thin connecting element 562 may be formed out of ceramic, composite or metal. The thin connecting element 562 may have a recess 564 that mates with a projection portion 566 of the slip ring 512 (or 504). Connecting element 562 is located adjacent to the breaking element 560 and is configured to engage with the breaking element 560. In this case, the one-piece slip ring may be retained by a retaining mechanism 550 located on the wedge, as illustrated in FIG. 12, but would not be able to deploy until the breaking element 560, on the adjacent part, breaks the connecting element 562. The connecting element 562 may also be initially separated from the slip ring 512 (or 504), and engaged into the segmented slip ring during assembly.

According to another embodiment illustrated in FIGS. 14A-14D, a retaining mechanism 1440 is located between (1) the slip ring 512 and (2) the mule shoe 518 or the push ring 503. Retaining mechanism 1440 may be implemented as a slip cage 1440A having a shear tab 1440B that mates with the slip ring 512 as shown in FIG. 14A. While FIG. 14A shows a cross-section through the slip cage and the shear tab, FIG. 14B shows a top view of this arrangement. Note that slip cage 1440A in FIG. 14B is shown also having a slip alignment arm 1440C, which maintain an alignment between the plural parts 512A. FIG. 14B shows only two parts 512A, but a slip ring may have more than two parts. One skilled in the art would understand that when the wedge 510 moves toward the mule shoe 518 or push ring 503, the slip alignment arm 1440C guides the parts 512A so that these parts substantially maintain a similar gap between them. Retaining mechanism, (the shear tab 1440B) is likely to break during the setting process, so that the various parts 512B are released from it.

FIG. 14A also shows a shear band 1442 that is located between the slip ring 512 and the wedge 510. Shear band 1442 may be shaped like a band and it may have one portion mating with a groove 512B formed in the slip ring 512 and another portion mating with a groove 510A formed in the wedge 510. The shear band 1442, similar to the shear tab 1440B, may be made of a material that shear when pressure is applied by the wedge, to release the parts of the slip ring. In one embodiment, the shear band may be integrally formed with the wedge. In one application, the slip cage 1440A and the shear band 1442 extend all around the mandrel. FIG. 14C shows another cross-section through the plug, but this cross-section is slightly rotated relative to the cross-section of FIG. 14A, to show the slip alignment arm 1440C. FIG. 14D is a top view of the plug.

According to this embodiment, when the setting tool applies a force to the mandrel and also to the push ring, the breaking element 560 will be squeezed between the wedge and the push ring or between the wedge and the mule shoe until the breaking elements breaks the connecting element 562 into pieces. However, until the connecting element 562 is in one piece, the orientation of the various slip ring parts 512A (or 504A) relative to a longitudinal axis of the casing is maintained so that it more likely that the spaces that will be formed between the slip ring parts when the plug is set, is uniform.

A method for manufacturing one or more of the above discussed downhole tools is now discussed with regard to FIG. 15. The method includes a step 1500 of adding a push ring 503 to a mandrel 502, a step 1502 of adding a first slip ring 504 to the mandrel, adjacent to the push ring 503; a step 1504 of adding a first wedge 506 to the mandrel, adjacent to the first slip ring 504; a step 1506 of adding a sealing element 508 to the mandrel, for sealing the well, and located adjacent to the first wedge 504; a step 1508 of adding a second wedge 510 to the mandrel, adjacent to the sealing element 508; a step 1510 of adding a second slip ring 512 to the mandrel, adjacent to the second wedge 510; a step 1512 of adding a mule shoe 518 to the mandrel, adjacent to the second slip ring 512; and a step 1514 of making a retaining mechanism (530, 540) in at least one of the push ring 503, the first wedge 506, the second wedge 510, and the mule shoe 518. When the first slip ring 504 and/or the second slip ring 512 are added to the mandrel, they fit into the retaining mechanism. The retaining mechanism is built in such a way that is part of (1) either the first slip ring 504 or the second slip ring 512, or (2) one of the push ring 503, the first wedge 506, the second wedge 510, or the mule shoe 518, but not both (1) and (2). In other words, the retaining mechanism does not connect in a unitary way a slip ring and another component of the plug.

A method for using one of the plugs discussed above is now presented with regard to FIG. 16. In step 1600, a plug is provided and the plug has a retaining mechanism located between a slip ring and one of the components of the plug, e.g., push ring, wedge, mule shoe. The plug is lowered into a well in step 1602 and in step 1604 a setting tool, which is attached to the plug, is instructed to set the plug. During this step, the retaining mechanism, which retains the slip ring to the plug, breaks apart due to the pressure exerted by the wedge, and parts of the slip ring separate from each other and are pushed against the well to set the plug.

The disclosed embodiments provide methods and systems for providing a plug with improved slip ring deployment. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.

Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.

This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims. 

What is claimed is:
 1. A downhole tool for sealing a well, the downhole tool comprising: a push ring; a first slip ring located adjacent to the push ring; a first wedge located adjacent to the first slip ring and configured to push the first slip ring and separate the first slip ring into parts; and a retaining mechanism configured to retain the first slip ring next to one of the push ring or the first wedge, wherein the retaining mechanism is part of either (1) the first slip ring or (2) the one of the push ring or the first wedge, but not both.
 2. The downhole tool of claim 1, wherein the retaining mechanism is part of the push ring.
 3. The downhole tool of claim 1, wherein the retaining mechanism is part of the first wedge.
 4. The downhole tool of claim 1, wherein the retaining mechanism is part of the first wedge and the retaining mechanism is located under the first slip ring.
 5. The downhole tool of claim 1, wherein the retaining mechanism is independent and located at an interface between the first wedge and the first slip ring.
 6. The downhole tool of claim 1, wherein the retaining mechanism is part of the push ring and there is an additional retaining mechanism that is part of the wedge.
 7. The downhole tool of claim 1, wherein the slip ring has a first number “n” of slip ring parts and the retaining mechanism has a number “m” of parts, and m is smaller than n.
 8. The downhole tool of claim 1, wherein the slip ring has a first number “n” of slip ring parts and the retaining mechanism has a number “m” of parts, and m is equal to n.
 9. The downhole tool of claim 1, wherein the slip ring is made as a single, integral piece.
 10. The downhole tool of claim 1, wherein the slip ring is made of plural individual elements that are hold together by the retaining mechanism.
 11. The downhole tool of claim 1, wherein the retaining mechanism has a first part located on the first wedge and a second part located on the first slip ring.
 12. The downhole tool of claim 11, wherein the first part engages the second part in a locking configuration.
 13. The downhole tool of claim 11, wherein the first part is a tongue and the second part is a groove.
 14. The downhole tool of claim 1, further comprising: a breaking mechanism located next to the retaining mechanism, and configured to break the retaining mechanism when the downhole tool is set, wherein the retaining mechanism is attached to the first slip ring and configured to keep parts of the first slip ring together.
 15. The downhole tool of claim 1, further comprising: a sealing element for sealing the well and located adjacent to the first wedge; a second wedge located adjacent to the sealing element; a second slip ring located adjacent to the second wedge; and a mule shoe located adjacent to the second slip ring.
 16. A downhole tool for sealing a well, the downhole tool comprising: a mule shoe; a first slip ring located adjacent to the mule shoe; a first wedge located adjacent to the first slip ring and configured to push the first slip ring and separate the first slip ring into parts; and a retaining mechanism configured to retain the first slip ring next to one of the first wedge and the mule shoe, wherein the retaining mechanism is part of either (1) the first slip ring or (2) one of the first wedge and the mule shoe, but not both.
 17. The downhole tool of claim 16, wherein the retaining mechanism is part of the mule show.
 18. The downhole tool of claim 16, wherein the retaining mechanism is part of the first wedge.
 19. The downhole tool of claim 16, wherein the retaining mechanism is part of the first wedge and the retaining mechanism is located under the first slip ring.
 20. The downhole tool of claim 16, wherein the retaining mechanism is independent and located at an interface between the first wedge and the first slip ring.
 21. The downhole tool of claim 16, wherein the retaining mechanism is part of the mule shoe and there is an additional retaining mechanism that is part of the first wedge.
 22. The downhole tool of claim 16, further comprising: a breaking mechanism located adjacent to the retaining mechanism and configured to break the retaining mechanism when the downhole tool is set, wherein the retaining mechanism is attached to the first slip ring and configured to keep parts of the first slip ring together.
 23. The downhole tool of claim 16, further comprising: a push ring; a second slip ring located adjacent to the push ring; a second wedge located adjacent to the second slip ring and configured to push the second slip ring; and a sealing element for sealing the well and located between the first wedge and the second wedge.
 24. The downhole tool of claim 23, wherein the first and second wedges are configured to squeeze the sealing element to extend radially and each of the first and second wedges are configured to break the first and second slip rings, respectively.
 25. The downhole tool of claim 16, wherein the mule shoe, the first slip ring, and the first wedge are located on this order on a mandrel.
 26. The downhole tool of claim 16, wherein the slip ring is made as a single, integral piece.
 27. The downhole tool of claim 16, wherein the slip ring is made of plural individual elements that are hold together by the retaining mechanism.
 28. A downhole tool for sealing a well, the downhole tool comprising: a push ring; a first slip ring located adjacent to the push ring; a first wedge located adjacent to the first slip ring and configured to push the first slip ring; a sealing element for sealing the well and located adjacent to the first wedge; a second wedge located adjacent to the sealing element; a second slip ring located adjacent to the second wedge; a mule shoe located adjacent to the second slip ring; and a retaining mechanism configured to connect at least one of the first slip ring and the second slip ring to one of the push ring, the first wedge, the second wedge and the mule shoe, wherein the retaining mechanism is part of either (1) the first slip ring or the second slip ring, or (2) one of the push ring, the first wedge, the second wedge or the mule shoe, but not both.
 29. A downhole tool for sealing a well, the downhole tool comprising: a slip ring located on a mandrel; a wedge located adjacent to the slip ring; a retaining mechanism located adjacent to the slip ring and configured to maintain the slip ring attached to the mandrel; and an element located adjacent to the retaining mechanism, wherein the retaining mechanism is independent of the slip ring, the wedge and the element.
 30. The downhole of claim 29, wherein the retaining mechanism is a cage extending all around the mandrel.
 31. The downhole of claim 29, wherein the retaining mechanism includes a cage, a shear tab for each independent part of the slip ring, the shear tab being attached to the cage.
 32. The downhole of claim 31, further comprising: a shear band located between the slip ring and the wedge.
 33. The downhole of claim 32, wherein the shear band has a first portion that enters a groove of the slip ring and a second portion that enters a groove of the wedge.
 34. The downhole of claim 33, wherein the shear band and the shear tab break to release the independent part.
 35. A method for using a plug in a well, the method comprising: providing the plug with a retaining mechanism located between a slip ring and one of a wedge, mule shoe and push ring; lowering the plug into the well; setting the plug into the well by activating a setting tool, which results in parts of the slip ring to move away from each other, wherein the retaining mechanism is configured to guide the parts of the slip ring to maintain a substantially uniform gap between the parts. 